Portfolio Essay Genetics

5/13/2011

DNA and RNA are abbreviations for deoxyribose and ribose nucleic acids. DNA and RNA are polypeptides composed of long chains of nucleotide monomers. These nucleic acids are polymers that serve as the blueprints for constructing proteins. Their monomers are called nucleotides. There are five kinds of nucleotides, each is made of a five-carbon sugar, a phosphate group, and one nitrogenous base. The five kinds of nucleotides are; adenine, guanine, cytosine, thymine, and uracil. However, thymine is only found in DNA and uracil is only found in RNA. A polynucleotide is formed when dehydration synthesis occurs between one nucleotide and the sugar of another. This results in a repeating S - P backbone. DNA is double-stranded (double-helix) RNA is single stranded. Despite the different number of strands and the difference of uracil in RNA, DNA and RNA have virtually the same structure. The both have a sugar-phosphate backbone, and nitrogenous bases. In DNA, the base pairs are complementary so that the DNA is even in diameter all the way down its length. The complimentary nitrogenous bases pair as follows: guanine only bonds to cytosine and thymine only binds to adenine accept uracil replaces thymine in RNA. Uracil replaces thymine because uracil takes less energy to make, but is not as stable.

DNA replication is a complicated process that is dependent on specific base pairing. The Central Paradigm is what some call the conversion process from DNA to RNA to Protein. Genetic information is written as codons. Codons are groups of three nitrogenous bases. The information that is stored on a DNA molecule needs to be used to create proteins. DNA cannot leave the nucleus in eukaryotic organisms because the molecule is to large to move through the nuclear membrane. There is 20 amino acids and 4 base pairs. The process of transcription is the making of Messenger RNA (mRNA) off of the DNA molecule. Transcription occurs when information that is stored in the base sequences of DNA is transcribed to make single-strand of messenger RNA (mRNA). In other words, the DNA's code is rewritten as mRNA. The mRNA molecule is made from just one of the strands of the DNA molecule because the other side is used to produce transfer RNA (tRNA). The mRNA is able to leave the nucleus so that it can create the necessary proteins in the cytosol. The mRNA is complementary to the section of DNA it was copied from accept for how it has uracil instead of thymine. DNA is essentially the template for creating the proteins that the cell needs to grow, function and survive. The RNA nucleotides are linked by transcription enzyme called RNA Polymerase. RNA polymerase must be told where to start and where to stop the transcribing process. The start signal is the promoter area of DNA, the promoter is a sequence of bases called a TATA box. TAC is the 'start' codon which sets the triplet code. The first phase of transcription is triggered when a specific hormone or signal protein enters the nucleus as a message that a specific protein section of the DNA is needed. The enzyme RNA polymerase attaches to the promoter of DNA. For any gene, the promoter region signals only one of the two strands to be transcribed. This is the lead strand of DNA, this is where mRNA are made. The other strand of DNA is the lag strand, where tRNA is made. RNA elongates as RNA polymerase assembles it in sequence complimentary to DNA. Finally RNA polymerase reaches a section on the DNA lead strand called the terminator. The terminator signals the end of the gene and causes the RNA polymerase to detach. The DNA strand reforms a double helix and the mRNA is released. Genetic messages are translated in the Cytoplasm. Messenger RNA conveys the genetic information from DNA in the nucleus to the translation devices in the cell's cytoplasm. The mRNA and tRNA leaves the nucleus and enters the cytoplasm if the organism is a eukaryote, if the organism is a prokaryote, the mRNA simply stays in the cytoplasm where it is because prokaryotic organisms have no nuclear membrane or nucleus to contain their cell's DNA. The tRNA is a molecular interpreter that translates base sequences to a proper amino acid. In living cells, amino acids are either synthesized or obtained from food. The tRNA picks up the appropriate amino acid and then recognizes the appropriate mRNA codon to place the amino acids in the right sequence.

One of the difficulties that I had at first with DNA replication was that not all of the DNA is used to produce a single protein, but once I realized the part about the start and stop codon meant that there could be multiple start and stop codons on a single DNA strand, it all became clear to me. The best tool for learning DNA transcription and translation were videos on the internet. They were the largest help for me to learn about this topic because I was able to hear what the molecules were and what they do as I watched them do it. The only bad thing about the videos was that most of them had different animation where some had molecule-looking models and others had symbolic shapes for each molecule and organelle.

The knowledge that I acquired during this thematic area of study such as the structure of DNA reveals many things about the biological world that we live in and study. It shows how organisms are able to grow and reproduce – key aspects in determining whether or not a chemical reaction is alive or not, because in reality, that is all that life is.

URLs of helpful internet videos:

http://www.youtube.com/watch?v=vJSmZ3DsntU

http://www.youtube.com/watch?v=WsofH466lqk

http://www.youtube.com/watch?v=983lhh20rGY

http://www.youtube.com/watch?v=41_Ne5mS2ls